Vane pump

ABSTRACT

A vane pump includes a rotor; a plurality of vanes; a cam ring; a second side plate; a suction port provided in the second side plate, the suction port being configured to guide working fluid to the pump chambers; a pump cover arranged so as to sandwich the second side plate with the cam ring; and a low-pressure chamber formed in the pump cover, the low-pressure chamber having an opening portion communicating with the suction port. The suction port is arranged so as to be shifted towards a forward side of in a rotating direction of the rotor with respect to the opening portion of the low-pressure chamber.

TECHNICAL FIELD

The present invention relates to a vane pump.

BACKGROUND ART

JP2014-74368A discloses a vane pump including a rotor that is driven rotationally, a plurality of vanes provided on the rotor, and a cam ring that accommodates the rotor. The vanes reciprocate as the rotor is rotated, and tip end portions of the vanes slide along an inner circumferential cam face of the cam ring. A pair of side plates are provided on both sides of the rotor and the cam ring, and the pair of side plates define pump chambers that are partitioned by the plurality of vanes between the rotor and the cam ring.

The vane pump disclosed in JP2014-74368A further includes a pump cover that is arranged so as to sandwich one of the side plates with the cam ring. A low-pressure chamber is formed by the pump cover, and suction ports are provided in the one of the side plates. Working fluid is sucked into the pump chambers from the low-pressure chamber through the suction ports.

SUMMARY OF INVENTION

In a vane pump, pump chambers rotate together with vanes. Therefore, when working fluid in a low-pressure chamber is sucked into the pump chambers, forward-side portions of the pump chambers in the rotating direction are less likely to be filled with the working fluid. Therefore, as the rotation speed of the pump is increased, the working fluid tends not to be distributed to the forward-side portions of the pump chambers in the rotating direction due to stagnation of the working fluid. As a result, cavitation may be caused due to insufficiency of the working fluid with respect to the volume of the pump chambers. For such a reason, there is a requirement for the vane pump having an improved suction property.

An object of the present invention is to improve a suction property of a vane pump.

According to one aspect of the present invention, a vane pump includes: a rotor configured to be driven rotationally; a plurality of vanes provided on the rotor so as to be able to reciprocate in a radial direction of the rotor; a cam ring accommodating the rotor, the cam ring having an inner circumferential cam face on which tip ends of the plurality of vanes slide by rotation of the rotor; a side member brought into contact with an end surface of the cam ring, the side member being configured to define pump chambers partitioned by the plurality of vanes between the rotor and the cam ring; a suction port provided in the side member, the suction port being configured to guide working fluid to the pump chambers; a cover member arranged so as to sandwich the side member with the cam ring; and a low-pressure chamber formed in the cover member, the low-pressure chamber having an opening portion communicating with the suction port. The suction port is arranged so as to be shifted towards a forward side of in a rotating direction of the rotor with respect to the opening portion of the low-pressure chamber.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a sectional view of a vane pump according to an embodiment of the present invention;

FIG. 2 is a sectional view taken along a line II-II in FIG. 1;

FIG. 3 is a plan view of a rotor, vanes, and a cam ring viewed from a pump cover side;

FIG. 4 is a sectional view of the cam ring, and first and second side plates;

FIG. 5 is a plan view of the first side plate viewed from the cam ring side;

FIG. 6 is a plan view of the second side plate viewed from the cam ring side;

FIG. 7 is a plan view of the rotor, the vanes, the cam ring, and the second side plate viewed from the pump body side;

FIG. 8 is a plan view of the rotor, the vanes, the cam ring, and the second side plate viewed from the pump body side, and a low-pressure chamber is shown with two-dot chain line;

FIG. 9 is a sectional view taken along a line IX-IX in FIG. 8; and

FIG. 10 is a sectional view of the vane pump according to another embodiment of the present invention, and shows the vane pump in a manner corresponding to FIG. 9.

DESCRIPTION OF EMBODIMENTS

A vane pump 100 according to an embodiment of the present invention will be described below with reference to the drawings. Although description is given to the vane pump 100 using working oil as working fluid, other fluid such as working water etc. may also be used as the working fluid.

FIGS. 1 and 2 are sectional views of the vane pump 100. FIG. 1 shows the sectional view taken along a line I-I in FIG. 2, and FIG. 2 shows the sectional view taken along a line II-II in FIG. 1. The vane pump 100 is used as a hydraulic source for a hydraulic apparatus 1 mounted on a vehicle (for example, a power steering apparatus, a transmission, and so forth).

The vane pump 100 includes a driving shaft 10, a rotor 20 that is linked to the driving shaft 10, a plurality of vanes 30 that are provided on the rotor 20, and a cam ring 40 that accommodates the rotor 20 and the vanes 30.

The driving shaft 10 is rotatably supported by a pump body 50 and a pump cover (cover member) 60. As motive force from an engine or an electric motor (not shown) is transmitted to the driving shaft 10, the rotor 20 is rotated by the rotationally driven driving shaft 10.

In the following, the rotation center axial direction of the rotor 20, the radial direction of the rotor 20, and the rotating direction of the rotor 20 will be referred to simply as “the axial direction”, “the radial direction”, and “the rotating direction”, respectively.

FIG. 3 is a plan view of the rotor 20, the vanes 30, and the cam ring 40 viewed from the pump cover 60 side. As shown in FIG. 3, in the rotor 20, a plurality of slits 22 each having an opening portion 21 on an outer circumferential surface of the rotor 20 are formed in a radiating pattern with predetermined gaps therebetween. The opening portions 21 of the slits 22 are formed at raised portions 23 that protrude outwards in the radial direction from an outer circumference of the rotor 20. In other words, the number of the raised portions 23 formed on the outer circumference of the rotor 20 corresponds to that of the slits 22. In each of the slits 22, a back pressure chamber 24 is defined by the vane 30.

The vanes 30 are respectively pushed into the slits 22 in a freely slidable manner and reciprocate in the radial direction together with the rotation of the rotor 20. Tip end portions 31 of the vanes 30 face against an inner circumferential surface 40 a of the cam ring 40, and base-end portions 32 of the vanes 30 respectively face against the back pressure chambers 24.

The working oil is guided into the back pressure chambers 24. The vanes 30 are pushed by the pressure of the working oil in the back pressure chambers 24 in the directions in which the vanes 30 protrude out from the slits 22, and the tip end portions 31 of the vanes 30 come to contact with the inner circumferential surface 40 a of the cam ring 40.

Referring again to FIGS. 1 and 2, the vane pump 100 further includes first and second side plates 70 and 80 serving as first and second side members that are arranged such that the rotor 20 and the cam ring 40 are positioned between the first and second side plates 70 and 80 in the axial direction.

FIG. 4 is a sectional view of the cam ring 40 and the first and second side plates 70 and 80. In FIG. 4, a high-pressure chamber 53, passages 54, and a low-pressure chamber 61, which will be described later, are shown with two-dot chain line.

As shown in FIG. 4, the first and second side plates 70 and 80 have side surfaces 70 a and 80 a, respectively, that are brought into contact with the rotor 20 and the cam ring 40 and define pump chambers 41 partitioned by the vanes 30 between the rotor 20 and the cam ring 40.

As shown in FIG. 3, the inner circumferential surface 40 a of the cam ring 40 is formed to have a substantially oval shape. In the following, the inner circumferential surface 40 a may also be referred to as “an inner circumferential cam face 40 a”.

Because the inner circumferential cam face 40 a of the cam ring 40 is formed to have a substantially oval shape, the vanes 30 reciprocates with respect to the rotor 20 along with the rotation of the rotor 20, and the pump chambers 41 are expanded and contracted repeatedly. The working oil is sucked into the pump chambers 41 when the pump chambers 41 are expanded, and the working oil is discharged from the pump chambers 41 when the pump chambers 41 are contracted.

In this embodiment, as the rotor 20 completes a full rotation, the vanes 30 reciprocate twice, and the pump chambers 41 repeat the expansion and contraction twice. In other words, the vane pump 100 has two expansion regions 42 a and 42 c where the pump chambers 41 are expanded and two contraction regions 42 b and 42 d where the pump chambers 41 are contracted in an alternate manner in the rotating direction.

As shown in FIGS. 1 and 2, the pump body 50 has an accommodating concave portion 51 for accommodating the rotor 20, the cam ring 40, and the first side plate 70. The first side plate 70 is arranged on a bottom surface 51 a of the accommodating concave portion 51.

An annular groove 52 is formed in the bottom surface 51 a of the accommodating concave portion 51. The high-pressure chamber 53 into which the working oil that has been discharged from the pump chambers 41 flows is defined by the annular groove 52 and the first side plate 70. The high-pressure chamber 53 is connected to the hydraulic apparatus 1, and the working oil that has been discharged from the pump chambers 41 is supplied to the hydraulic apparatus 1 through the high-pressure chamber 53.

FIG. 5 is a plan view of the first side plate 70 viewed from the cam ring 40 side. As shown in FIGS. 4 and 5, the first side plate 70 is formed so as to have an annular shape having a hole 71 at its center. The driving shaft 10 is inserted into the hole 71 (see FIG. 1).

On the first side plate 70, two discharge ports 72 are provided for guiding the working oil discharged from the pump chambers 41 to the high-pressure chamber 53. The discharge ports 72 are respectively located in the contraction regions 42 b and 42 d. Therefore, the working oil in the pump chambers 41 is discharged to the high-pressure chamber 53 through the discharge ports 72 when the pump chambers 41 pass through the contraction regions 42 b and 42 d.

In addition, in the first side plate 70, two back-pressure passages 73 are formed for guiding the working oil from the high-pressure chamber 53 to the back pressure chambers 24. The back-pressure passages 73 have arc shapes centered at the hole 71 and are located in the expansion regions 42 a and 42 c. Therefore, the working oil is guided from the high-pressure chamber 53 to the back pressure chambers 24 passing through the expansion regions 42 a and 42 c. As a result, the vanes 30 passing through the expansion regions 42 a and 42 c are pushed by the pressure in the back pressure chambers 24 in the directions in which the vanes 30 protrude out from the slits 22 (see FIG. 3).

As described above, the vanes 30 are pushed in the directions in which the vanes 30 protrude out from the slits 22 by the pressure in the back pressure chambers 24 and by a centrifugal force caused by the rotation of the rotor 20.

Referring again to FIGS. 1 and 2, the accommodating concave portion 51 of the pump body 50 is formed so as to be larger relative to the cam ring 40, and the passages 54 are defined by the cam ring 40 and the pump body 50. The passages 54 extend from an outer circumference of the second side plate 80 to an outer circumference of the first side plate 70.

An opening portion of the accommodating concave portion 51 is closed by the pump cover 60. The pump cover 60 is fastened to the pump body 50 by bolts (not shown). The second side plate 80 is arranged between the pump cover 60 and the cam ring 40.

The pump cover 60 forms the low-pressure chamber 61 that is connected to a tank 2. The low-pressure chamber 61 communicates with a low-pressure passage 55 formed in the pump body 50. The working oil in the tank 2 is supplied to the low-pressure chamber 61 through the low-pressure passage 55.

In addition, the low-pressure chamber 61 communicates with the passages 54 and has opening portions 62 that respectively communicate with suction ports 81 provided in the second side plate 80. The passages 54 respectively communicate with suction ports 74 that guide the working oil to the pump chambers 41. In other words, the working oil in the low-pressure chamber 61 is guided to the pump chambers 41 through the passages 54 and the suction ports 74.

In this embodiment, as shown in FIGS. 4 and 5, the suction ports 74 are defined by recessed portions 75 formed in the side surface 70 a of the first side plate 70 and an end surface 40 b of the cam ring 40 that faces against the recessed portions 75. The suction ports 74 may by formed by holes penetrating through the first side plate 70, for example.

FIG. 6 is a plan view of the second side plate 80 viewed from the cam ring 40 side, and FIG. 7 is a plan view of the rotor 20, the vanes 30, the cam ring 40, and the second side plate 80 viewed from the pump body 50 side.

As shown in FIGS. 4, 6, and 7, the second side plate 80 has two recessed portions 82 formed in an outer circumferential surface 80 b. The recessed portions 82 communicate with the pump chambers 41 through opening portions 83 a formed in the side surface 80 a of the second side plate 80. In addition, the recessed portions 82 communicates with the low-pressure chamber 61 through opening portions 83 b formed in a side surface 80 c on the opposite side of the side surface 80 a of the second side plate 80.

The recessed portions 82 are respectively located in the expansion regions 42 a and 42 c. Therefore, when the pump chambers 41 pass through the expansion regions 42 a and 42 c, the working oil is guided to the pump chambers 41 from the low-pressure chamber 61 through the recessed portions 82.

As described above, the suction ports 81 are defined by the recessed portions 82 and an end surface 40 c of the cam ring 40 that faces against the recessed portions 82 and guide the working oil to the pump chambers 41 by directing flows of the working oil from the low-pressure chamber 61 in the axial direction (the direction towards the cam ring 40 from the second side plate 80).

The configuration of the suction port 81 is not limited to that in which the suction port 81 is defined by the recessed portion 82 and the end surface 40 c of the cam ring 40, and the suction port 81 may have, for example, a configuration constituting hole penetrating through the second side plate 80.

FIG. 8 is a plan view of the rotor 20, the vanes 30, the cam ring 40, and the second side plate 80 viewed from the pump body 50 side, and the low-pressure chamber 61 is shown with two-dot chain line. FIG. 9 is a sectional view taken along a line IX-IX in FIG. 8. In FIG. 9, illustration of the rotor 20 and the vanes 30 is omitted.

As shown in FIGS. 8 and 9, the opening portions 83 a and 83 b of the suction ports 81 are formed so as to have substantially the same width in the rotating direction as that of the opening portions 62 of the low-pressure chamber 61. In addition, the opening portions 83 a and 83 b are located at the forward side in the rotating direction with respect to the opening portions 62 of the low-pressure chamber 61. In other words, the suction ports 81 are arranged so as to be shifted towards the forward side in the rotating direction with respect to the opening portions 62 of the low-pressure chamber 61.

The positions of the suction ports 81 and the opening portions 62 of the low-pressure chamber 61 are aligned by two dowel pins (not shown) provided on the pump cover 60 and two pin holes 84 provided in the second side plate 80 (see FIG. 6).

More specifically, each dowel pin extends in the axial direction from a contact surface 60 a of the pump cover 60 that is in contact with the second side plate 80. The pin holes 84 are formed so as to penetrate through the second side plate 80 in the axial direction. The position of the pump cover 60 is aligned in the circumferential direction with respect to the second side plate 80 by respectively inserting the dowel pins into the pin holes 84.

In this embodiment, the cam ring 40 has two pin holes 43 formed at positions corresponding to the pin holes 84 (see FIGS. 3, 7, and 8), and the first side plate 70 has two pin holes 76 formed at positions corresponding to the pin holes 43 (see FIG. 5). The pin holes 43 are formed so as to penetrate through the cam ring 40 in the axial direction, and the pin holes 76 are formed so as to penetrate through the first side plate 70 in the axial direction. In other words, the pin holes 84, 43, and 76 form through holes that penetrate from the second side plate 80 to the first side plate 70 through the cam ring 40. By respectively inserting the dowel pins into the pin holes 84, 43, and 76, it is possible to align the positions of the pump cover 60, the second side plate 80, the cam ring 40, and the first side plate 70.

The pin holes 84, 43, and 76 are formed so as to be shifted towards the forward side in the rotating direction from conventional positions (the positions of the pin holes 84 at which when the dowel pins are inserted into the pin holes 84, the positions of the opening portions 62 of the low-pressure chamber 61 coincide with those of the suction ports 81). Therefore, by inserting the dowel pins into the pin holes 84, 43, and 76, the suction ports 81 are arranged so as to be shifted towards the forward side in the rotating direction with respect to the opening portions 62 of the low-pressure chamber 61.

Because the suction ports 81 are positioned at the forward side in the rotating direction relative to the opening portions 62 of the low-pressure chamber 61, the flows of the working oil being guided from the low-pressure chamber 61 to the pump chambers 41 are directed towards the front side in the rotating direction by the suction ports 81. In other words, a flow velocity vector (inflow angle) is directed to the pump rotating direction. Therefore, when the working oil flowing from the low-pressure chamber 61 is sucked into the pump chambers 41, the working oil flows into the forward-side portions of the pump chambers 41 in the rotating direction. Therefore, the suction property of the vane pump 100 is improved, and the working oil is distributed even to the forward-side portions of the pump chambers 41 in the rotating direction. Because the working oil is guided to the pump chambers 41 at sufficient amount, it is possible to prevent lowering of pressure in the pump chambers 41 and to prevent occurrence of cavitation.

In the low-pressure chamber 61, wall surfaces 63 are formed so as to extend in the directions orthogonal to the rotating direction and such that the flows of the working oil in the low-pressure chamber 61 are directed to the axial direction and guided to the opening portions 62. Each of the wall surfaces 63 is inclined with respect to the axial direction so as to guide the working oil flowing out from the opening portion 62 towards the front side in the rotating direction. More specifically, the wall surface 63 is inclined with respect to the axial direction such that the opening portion 62 is positioned at the forward side in the rotating direction with respect to end portion 63 a on the opposite side of the opening portion 62 of the wall surface 63.

Because the wall surface 63 in the low-pressure chamber 61 directs the flows of the working oil flowing out from the opening portion 62 towards the front side in the rotating direction, when the working oil from the low-pressure chamber 61 is sucked into the pump chambers 41, stagnation of the working oil at the rearward-side portions of the pump chambers 41 in the rotating direction is unlikely to be caused. Therefore, the suction property of the vane pump 100 is improved, and it is possible to prevent occurrence of the cavitation.

Furthermore, the suction ports 81 are each arranged so as to be shifted towards the forward side in the rotating direction with respect to the imaginary extended surface of the wall surface 63 in the low-pressure chamber 61. More specifically, the opening portions 83 a and 83 b of each suction port 81 are positioned at the forward side in the rotating direction with respect to the imaginary extended surface of the wall surface 63 in the low-pressure chamber 61.

Because the suction ports 81 are positioned at the forward side in the rotating direction relative to the imaginary extended surfaces of the wall surfaces 63 in the low-pressure chamber 61, the flows of the working oil in the low-pressure chamber 61 are less likely to be inhibited by inner circumferential surfaces (side surfaces of the recessed portions 82) 81 a of the suction ports 81 after being directed by the wall surfaces 63 in the low-pressure chamber 61. Therefore, the forward-side portions of the pump chambers 41 in the rotating direction are filled with the working oil with higher reliability, and it is possible to further improve the suction property of the vane pump 100.

In this embodiment, although the inner circumferential surfaces 81 a of the suction ports 81 are formed so as to be in substantially parallel to the axial direction, as shown in FIG. 10, it is preferable that the inner circumferential surfaces 81 a of the suction ports 81 be formed so as to be inclined with respect to the axial direction so as to direct the flows of the working oil towards the front side in the rotating direction. More specifically, each of the inner circumferential surfaces 81 a of the suction ports 81 may be inclined with respect to the axial direction such that the opening portion 83 a of the suction port 81 is positioned at the forward side in the rotating direction with respect to the opening portion 83 b of the suction port 81.

The inner circumferential surfaces 81 a of the suction ports 81 are inclined with respect to the axial direction, and thereby, the flows of the working oil being guided from the low-pressure chamber 61 to the pump chambers 41 are directed towards the front side in the rotating direction. Therefore, when the working oil from the low-pressure chamber 61 is sucked into the pump chambers 41, the forward-side portions of the pump chambers 41 in the rotating direction are filled with greater amount of the working oil. Therefore, the suction property of the vane pump 100 is improved, and it is possible to prevent occurrence of the cavitation.

In addition, in this embodiment, although the opening portions 83 a and 83 b of the suction ports 81 are formed so as to have substantially the same width in the rotating direction as that of the opening portions 62 of the low-pressure chamber 61, the opening portions 83 a and 83 b of the suction ports 81 may have greater width in the rotating direction than that of the opening portions 62.

The configuration of the wall surfaces 63 in the low-pressure chamber 61 is not limited to that in which the wall surfaces 63 are formed so as to be inclined with respect to the axial direction, and the wall surfaces 63 may be formed so as to coincide with the axial direction.

Next, an operation of the vane pump 100 will be described with reference to FIGS. 1 to 3.

When motive force from an engine or an electric motor (not shown) is transmitted to the driving shaft 10, the rotor 20 is rotated by the rotationally driven driving shaft 10. As the rotor 20 is rotated, the vanes 30 reciprocate with respect to the rotor 20, and the pump chambers 41 are repeatedly expanded and contracted.

The working oil in the tank 2 is guided to the pump chambers 41 passing through the expansion regions 42 a and 42 c through the low-pressure chamber 61, the passages 54, and the suction ports 74, and also through the low-pressure chamber 61 and the suction ports 81.

The flows of the working oil being guided to the pump chambers 41 through the suction ports 81 are directed towards the front side in the rotating direction by the suction ports 81. Therefore, the suction property of the vane pump 100 is improved, and it is possible to prevent occurrence of the cavitation.

When the pump chambers 41 pass through the contraction regions 42 b and 42 d, the working oil in the pump chambers 41 is discharged to the high-pressure chamber 53 and guided to the hydraulic apparatus 1. Because the occurrence of the cavitation is prevented, it is possible to supply the working oil to the hydraulic apparatus 1 at higher pressure and at greater flow rate.

In the following, configurations, actions, and effects of the embodiment of the present invention will be described collectively.

In this embodiment, the vane pump 100 includes: the rotor 20 that is driven rotationally; the plurality of vanes 30 that are provided on the rotor 20 so as to be able to reciprocate in the radial direction of the rotor 20; the cam ring 40 that accommodates the rotor 20 and has the inner circumferential cam face 40 a on which the tip end portions 31 of the plurality of vanes 30 slide by the rotation of the rotor 20; the second side plate 80 that is brought into contact with the end surface 40 c of the cam ring 40 and defines the pump chambers 41 that are partitioned by the plurality of vanes 30 between the rotor 20 and the cam ring 40; the suction ports 81 that are provided in the second side plate 80 and guide the working oil to the pump chambers 41; the pump cover 60 that is arranged so as to sandwich the second side plate 80 with the cam ring 40; and the low-pressure chamber 61 that is formed in the pump cover 60 and has the opening portions 62 communicating with the suction ports 81, and the suction ports 81 are arranged so as to be shifted towards the forward side in the rotating direction of the rotor 20 with respect to the opening portions 62 of the low-pressure chamber 61.

In this configuration, because the suction ports 81 are arranged so as to be shifted towards the forward side in the rotating direction of the rotor 20 with respect to the opening portions 62 of the low-pressure chamber 61, when the working oil in the low-pressure chamber 61 is sucked into the pump chambers 41 through the suction ports 81, the working oil flows towards the front side in the rotating direction of the rotor 20. Therefore, the forward-side portions of the pump chambers 41 in the rotating direction are filled with greater amount of the working oil. Therefore, it is possible to improve the suction property of the vane pump 100.

In addition, in this embodiment, in the vane pump 100, the low-pressure chamber 61 has the wall surfaces 63 that guide the working oil to the suction ports 81, and the wall surfaces 63 are inclined so as to guide the working oil from the low-pressure chamber 61 towards the front side in the rotating direction of the rotor 20.

In this configuration, because the wall surfaces 63 in the low-pressure chamber 61 guide the working oil from the low-pressure chamber 61 towards the front side in the rotating direction of the rotor 20, when the working oil is sucked into the pump chambers 41 through the suction ports 81, the working oil flows towards the front side in the rotating direction of the rotor 20 with reliability. Therefore, the forward-side portions of the pump chambers 41 in the rotating direction are filled with greater amount of the working oil with higher reliability, and it possible to further improve the suction property of the vane pump 100.

In addition, in this embodiment, in the vane pump 100, the suction ports 81 are arranged so as to be shifted towards the forward side in the rotating direction of the rotor 20 with respect to the imaginary extended surfaces of the wall surfaces 63 in the low-pressure chamber 61.

In this configuration, because the suction ports 81 are arranged so as to be shifted towards the forward side in the rotating direction of the rotor 20 with respect to the imaginary extended surfaces of the wall surfaces 63 in the low-pressure chamber 61, the respective flows of the working oil in the low-pressure chamber 61 are less likely to be inhibited by the inner circumferential surfaces 81 a of the suction ports 81 after being directed by the wall surfaces 63 in the low-pressure chamber 61. Therefore, the forward-side portions of the pump chambers 41 in the rotating direction are filled with the working oil with reliability, and it is possible to further improve the suction property of the vane pump 100.

In addition, in this embodiment, in the vane pump 100, the suction ports 81 respectively have the inner circumferential surfaces 81 a that are inclined so as to guide the working oil from the low-pressure chamber 61 towards the front side in the rotating direction of the rotor 20.

In this configuration, because the respective inner circumferential surfaces 81 a of the suction ports 81 guide the working oil from the low-pressure chamber 61 towards the front side in the rotating direction of the rotor 20, when the working oil is sucked into the pump chambers 41 through the suction ports 81, the working oil flows towards the front side in the rotating direction of the rotor 20 with higher reliability. Therefore, the forward-side portions of the pump chambers 41 in the rotating direction are filled with the working oil with reliability, and it is possible to further improve the suction property of the vane pump 100.

The embodiments of the present invention described above are merely illustration of some application examples of the present invention and not of the nature to limit the technical scope of the present invention to the specific constructions of the above embodiments.

The present application claims a priority based on Japanese Patent Application No. 2015-215973 filed with the Japan Patent Office on Nov. 2, 2015, all the contents of which are hereby incorporated by reference. 

1. A vane pump comprising: a rotor configured to be driven rotationally; a plurality of vanes provided on the rotor so as to be able to reciprocate in a radial direction of the rotor; a cam ring accommodating the rotor, the cam ring having an inner circumferential cam face on which tip ends of the plurality of vanes slide by rotation of the rotor; a side member brought into contact with an end surface of the cam ring, the side member being configured to define pump chambers partitioned by the plurality of vanes between the rotor and the cam ring; a suction port provided in the side member, the suction port being configured to guide working fluid to the pump chambers; a cover member arranged so as to sandwich the side member with the cam ring; and a low-pressure chamber formed in the cover member, the low-pressure chamber having an opening portion communicating with the suction port, wherein the suction port is arranged so as to be shifted towards a forward side of in a rotating direction of the rotor with respect to the opening portion of the low-pressure chamber.
 2. The vane pump according to claim 1, wherein the low-pressure chamber has a wall surface for guiding the working fluid to the suction port, and the wall surface is inclined so as to guide the working fluid from the low-pressure chamber towards a front side in the rotating direction of the rotor.
 3. The vane pump according to claim 2, wherein the suction port is arranged so as to be shifted towards a forward side in the rotating direction of the rotor with respect to an imaginary extended surface of the wall surface in the low-pressure chamber.
 4. The vane pump according to claim 1, wherein the suction port has an inner circumferential surface inclined so as to guide the working fluid from the low-pressure chamber towards a front side in the rotating direction of the rotor. 